# Quantitative Aptitude: Boats and Streams Questions Set 6

1. A boat takes half time in moving a certain distance downstream than upstream. What is the ratio between rate of boat in still water and rate of current?
2:3
3:1
2:1
3:5
None
Option B
Solution:
Let the distance be xkm.
Then
2x/(u+v) = x/ (u-v)
2u – 2v = u+v
u:v=3:1.
2. A boat covers a certain distance downstream in 2 hour, while it comes back in 2 1/2 hours. If the speed of the stream be 3 km/hr, what is the speed of the boat in still water?
20km/hr
23km/hr
27km/hr
30km/hr
None
Option C
Solution:
Speed downstream = (u + 3) km/hr
Speed upstream = (u- 3) km/hr
(u+ 3) *2 = (u- 3) *5/2
4u+12=5u-15
u=27km/hr.
3. If sum of upstream and downstream speed of a boat is 82 kmph, and the boat travels 105 km. upstream in 3 hr, Find the time taken by boat to cover 141 km downstream.
5hrs
4hrs
3hrs
2hrs
None
Option C
Solution:
Speed of Upstream =u-v
Speed of Downstream = u+v
u-v+u+v=82
2u=82
u=41km/hr.
41 – v = 105/3 = 35
v = 6 km/hr
then,
u + v= 141/t
41 + 6 = 141/t
t = 141/47 = 3 hrs.
4. A boatman goes 4 km against the current of the stream in 1 hour and goes 2 km along the current in 10 minutes. How long will it take to go 24 km in stationary water?
5hrs
3hrs
2hrs
6hrs
None
Option B
Solution:
Upstream=4/1=4km/hr
Downstream=2*60/10=12km/hr
Speed in still water=(12+4)/2
=16/2=8km/hr.
For 24 km time=24/8
=3hrs.
5. The speed of a boat in still water is 15 km/hr. It can go 30 km upstream and return downstream to the original point in 4 hrs 30 min. The speed of the stream is:
12km/hr
8km/hr
5km/hr
10km/hr
None
Option C
Solution:
D=t [(u2 – v2) /2u] 30 = 4 ½ *[(152 – v2) /2*15] 30=9/2 (225- v2)/30
200=225- v2
v2=25
v=5km/hr.
6. A boat takes 12 hr to travel a distance upstream and takes 6 hr to travel the same distance downstream. If the speed of the boat in still water is 4 kmph, then what is the speed of the stream?
5km/hr
1km/hr
3km/hr
2km/hr
None
Option B
Solution:
6(3+v) = 12(3-v)
18 +6v=36-12v
18v=18
v=1km/hr.
7. A man can row 8 km/hr in still water. If it takes him thrice as long to row up, as to row down the river, then the rate of current in the stream would be
6.5km/hr
4.5km/hr
4km/hr
5.5km/hr
None
Option C
Solution:
Ratio 3:1
u=8km/hr
(8-v)*3t = (8+v)*t
24-3v=8+v
4v=16
v=4km/hr.
8. A man can row three-quarters of a kilometer against the stream in 45/4 minutes and return in 15/2 minutes. The speed of the stream
1km/hr
3km/hr
5km/hr
4km/hr
None
Option A
Solution:
Upstream in 45/4min=3/4km
In 1 hr =3/4*4/45*60
=4km/hr.
Downstream in 15/2min=3/4km
In 1 hr=3/4*2/15*60
=6km/hr.
V=(6-4)/2
=2/2
=1km/hr.
9. A boat running downstream covers 28 kms in 7 hours, while for covering the same distance upstream it takes 4 hours. What is the speed of the boat in still water and ?
4km/hr
4.5km/hr
5km/hr
5.5km/hr
None
Option D
Solution:
Downstream=28/7=4km/hr
Upstream=28/4=7km/hr
Speed of the boat u=(4+7) /2
=11/2=5.5km/hr.
10. A man can row 8 km/hr in still water. If the river is running at 3 km/hr, it takes 3 hours more in upstream than to go downstream for the same distance. How far is the place?
27.5km
29km
31.5km
33km
None
Option A
Solution:
D=3 (82 -32)/(2*3)
=(55*3)/6
=27.5km.